AVI BioPharma has started a clinical trial involving systemic administration of their AVI-4658 Morpholino oligo targeted to modify splicing of exon 51 in the human Dystrophin pre-mRNA transcript, excluding exon 51 from the mature mRNA. This is an experimental therapeutic for some mutations causing Duchenne muscular dystrophy, designed to restore the reading frame and ameliorate the effects of a frame-shifting mutation. This study involves intravenous injection of an unmodified Morpholino (note: Morpholinos are also called PMO, an acronym for phosphorodiamidate Morpholino oligomer).